The present invention relates to a chain conveyor of the type comprising an endless conveyor belt sliding along guide means which develop along a predetermined path, wherein the conveyor belt comprises a first and a second drive chain formed by annular elements. The annular elements of one chain are connected to corresponding annular elements of the other chain by means of cross bars defining the surface of the conveyor belt. Drive means are also provided, comprising at least one drive wheel which drives a chain of the belt.
Chain conveyors, of the abovementioned type, are widely used in a number of areas due to their intrinsic features which allow them to support heavy loads and to operate in different environments.
In general, in chain conveyors of the known type, the whole conveyor belt is supported and guided by means of the same drive chains which slide along guide channels which surround part of the profile of the chain itself. Consequently chain conveyors of this type have a number of disadvantages due to their structure and the consequent manner of supporting and guiding the conveyor belt.
More particularly, the use of belt guide and slide elements in the form of a channel, or such as to surround substantially most of the profile of the rings of the chains, causes considerable dragging friction, not only due to the large surface of contact with the chains, but also to the additional friction caused by structural and assembly defects of the various parts which make up the system. In addition to the deformations caused by welding the cross bars to the chains, the inevitable irregularities of shape and size of the rings may cause greater friction against the guide surfaces and consequently require the use of more powerful drive assemblies, particularly for conveyors which develop along paths of considerable length or with extremely complex or spiral paths.
A further disadvantage consists in the excessive weight of the conveyor belt, due to the fact that the chains had to be dimensioned to resist the high drive stresses and due to the need to use cross bars with a considerable section in order to prevent their deformation and that of the conveyor belt itself on account of the long support distance of the bars, particularly in belts of greater width. Moreover, bars of greater section create once again greater weight for the belt to drive.
Furthermore, in known conveyors of the aforesaid type, in an attempt to reduce the friction between the chains and guide channels, a lubricating agent is poured into said channels. Said lubricant contaminates in many cases the product conveyed by the belt, also due to the fact that the conveying surface of the belt is formed by bars welded directly onto the rings of the chain, particularly if these bars are attached to the horizontal rings of the chain, and is therefore too close to said lubricated channels for guiding the chains.
The object of the present invention is to provide a chain conveyor belt, by means whereof it is possible to separate the drive function from that of supporting and guiding the belt, which are performed by separate parts, in this way allowing a considerable reduction in friction and hence the power required to drive the conveyor belt itself.
A further object of the present invention is to provide a chain conveyor of the aforementioned kind, by means of which it is possible to reduce the weight of the conveyor belt considerably, at the same time maintaining its good structural rigidity, in this way also aiding in further reducing the power required for the driving and sliding of the belt.
A further object of the present invention is that of providing a chain conveyor as defined above, wherein the width of the belt can be calculated wholly independently of the position of the guide elements, and of the drive chains, in this way achieving broad freedom of design and use of the conveyor belt.
Another object of the present invention is that of providing a chain conveyor wherein the risk of the lubricant contaminating the product conveyed by the belt is avoided.
These and other objects or advantages can be achieved with a chain conveyor provided with an improved guide system, according to the features of the main claim. In particular, the general solution concept consists in providing a chain conveyor of the type comprising two lateral chains whose annular elements are connected by cross bars, and wherein use is made of support and guide means which do not involve the drive chains, which comprise longitudinal support elements on which the conveyor belt slides, resting directly with the cross bars. The longitudinal belt support and slide elements can be positioned either inside or outside the drive chains, with the advantage of freeing completely the dimensioning of the belt from the positioning of the guide elements and of the drive chains, at the same time reducing the causes for friction and the surfaces of contact due to the sliding of the conveyor belt.
A chain conveyor according to the invention is moreover suitable for using cogged drive assemblies tangential to the chains, which can be advantageously arranged both in the plane of the conveyor belt, and in orthogonal planes.
A chain conveyor according to the invention can moreover be provided with elements for lateral centering of the chains, fully independent of the means of supporting and guiding the belt itself. This allows advantageous use of the guide system according to the invention, particularly in chain conveyors intended for use in cold-storage rooms, or in leavening or freezer rooms for food products, in which the formation of ice on traditional guides has always entailed serious problems, particularly when the conveyor is started up after a period of defrosting of the room, due to the tendency for ice to form in the guide channels and to block the sliding of the chains.